1. Field of the Invention
The present invention relates to a video signal processing system, and more particularly to a chrominance signal processing apparatus in a video signal processing system. This application is based on Korean patent application 98-57167, which is hereby incorporated by reference for all purposes.
2. Description of the Related Art
Generally, video signal processing systems include, for example, color televisions, video cassette tape recorders, and video color printers. In such a video signal processing system, a composite video signal is divided into a luminance signal and a chrominance signal. The chrominance signal is then processed by various processes such as a color gain control, a color hue control, and flesh tone control, etc. After being processed by such processes, the resultant chrominance signal is transformed, along with the luminance signal, to an original RGB signal which is, in turn, output. To this end, the video signal processing system should be equipped with not only a circuit for transforming the luminance and chrominance signals to an RGB signal format, but also a variety of chrominance signal control circuits for conducting various controls for the chrominance signal including a color gain control, a color hue control, and flesh tone control, etc. according to the user""s intention.
FIG. 1 is a block diagram schematically illustrating a digital color television receiver which is a video signal processing system as mentioned above. Referring to FIG. 1, a plurality of channels carrying television video signals are received by tuner 100 via an antenna 118. The tuner 100 allows a user to select a channel from a plurality of channels, and outputs the television video signals of the selected channel to an intermediate frequency (IF) demodulator 102. The IF demodulator 102 demodulates the television video signal received therein into an IF signal which is sent to an analog/digital (A/D) converter 104. In the A/D converter 104, the video signal outputted from the IF demodulator 102 in the IF-modulated state is converted to a digital signal using binary-sampling in a pulse code modulation (PCM) fashion. A comb filter 106 receives the digital data from the A/D converter 104 and separates a luminance signal Y and a chrominance signal C from the received digital data. The chrominance signal C from the comb filter 106 is applied to a chrominance signal demodulator 108 which demodulates the received chrominance signal C into an R-Y chrominance signal Cr and a B-Y chrominance signal Cb. A color gain controller 110 receives the chrominance signals Cr and Cb from the chrominance signal demodulator 108, conducts a color gain control for those received signals, and outputs the resultant signals, namely, gain-controlled chrominance signals Cb_g and Cr_g, to a color hue controller 112. The color hue controller 112 controls the gain-controlled chrominance signals Cb_g and Cr_g in accordance with a color hue control coefficient, and then outputs the resultant signals, namely, hue-controlled chrominance signals Cb_h and Cr_h, to a flesh tone controller 114. In the flesh tone controller 114, the hue-controlled chrominance signals Cb_h and Cr_h are controlled in terms of flesh tone in accordance with a flesh tone control coefficient. The resultant signals, namely, flesh tone-controlled chrominance signals Cb_f and Cr_f, are applied to an RGB transform unit 116. The RGB transform unit 116 processes the flesh tone-controlled chrominance signals Cb_f and Cr_f along with the luminance signal Y, thereby transforming these signals to an original RGB signal which is finally outputted.
FIGS. 2, 4, and 6 illustrate detailed circuit configurations of the color gain controller 110, color hue controller 112 and flesh tone controller 114, respectively. Now, the operations of these controllers will be described in more detail, in conjunction with FIGS. 2, 4, and 6.
FIG. 2 is a block diagram illustrating a detailed circuit configuration of the color gain controller 110. As shown in FIG. 2, the color gain controller 110 multiplies the chrominance signals Cb and Cr received from the chrominance signal demodulator 108 of FIG. 1 by a color gain control coefficient G received from a multiplier 200, respectively. That is, the color gain controller 110 serves to vary the value of a vector A representing the chrominance signal C in proportion to the gain control coefficient G, as shown in FIG. 3 illustrating a color vector diagram of the chrominance signal C with the chrominance signal Cb as an abscissa and the chrominance signal Cr as an ordinate. The values of output signals from the color gain controller 110 respectively associated with the luminance signal Y and chrominance signals Cb and Cr can be expressed as follows:
Y=Y
Cbxe2x80x94g=Cbxc3x97G
Crxe2x80x94g=Crxc3x97Gxe2x80x83xe2x80x83[Equation 1]
The above Equation 1 may be expressed in the form of a matrix equation as follows:                               [                                                    Y                                                                    Cb_g                                                                    Cr_g                                              ]                =                              [                                                            1                                                  0                                                  0                                                                              0                                                  G                                                  0                                                                              0                                                  0                                                  G                                                      ]                    xc3x97                      [                                                            Y                                                                              Cb                                                                              Cr                                                      ]                                              [Equation  1a]            
In the above Equation 1a, xe2x80x9cCbxe2x80x9d represents a normalized value of the B-Y chrominance signal, xe2x80x9cCrxe2x80x9d represents a normalized value of the R-Y chrominance signal, and xe2x80x9cGxe2x80x9d represents the color gain control coefficient.
FIG. 4 is a block diagram illustrating a detailed circuit configuration of the color hue controller 112. As shown in FIG. 4, the color hue controller 112 serves to rotate or shift the coordinate axes of the chrominance signals Cb and Cr, as shown in FIG. 5, thereby achieving a variation in color. The hue of the chrominance signals Cb and Cr, which is the color represented by the color vector A, as shown in FIG. 5, may often be unacceptable to the viewer due to an inadequate chrominance signal phase sampling or a particular visual response of the viewer. In such a case, the viewer adjusts the hue of the chrominance signals Cb and Cr by varying the rotation angle or phase angle of the color vector A, while observing the display state of the television receiver, until a desired hue is obtained. In accordance with a viewer""s adjustment of the hue, the coordinate axes of the chrominance signals Cb and Cr are rotated or shifted, thereby controlling the hue of the color vector A.
When the viewer shifts the coordinate axes of the chrominance signals Cb and Cr by an angle of xcex8 in order to obtain a desired hue, the color hue control coefficient is set to xe2x80x9cxcex8xe2x80x9d. In this case, a color hue control coefficient value of xe2x80x9ccos xcex8xe2x80x9d or xe2x80x9cxe2x88x92sin xcex8xe2x80x9d is input to the color hue controller 112 via a first switch 402 which is coupled to the values xe2x80x9ccos xcex8xe2x80x9d and xe2x80x9cxe2x88x92sin xcex8,xe2x80x9d associated with the chrominance signals Cb and Cr, respectively. Another color hue control coefficient value of xe2x80x9csin xcex8xe2x80x9d or xe2x80x9ccos xcex8xe2x80x9d is input to the color hue controller 112 via a second switch 408 which is coupled to the values xe2x80x9csin xcex8xe2x80x9d and xe2x80x9ccos xcex8,xe2x80x9d associated with the chrominance signals Cb and Cr, respectively. In a first multiplier 400, the chrominance signal Cb, which is input to the color hue controller 112, is multiplied by xe2x80x9ccos xcex8xe2x80x9d applied to the first multiplier 400 in accordance with a switching operation of the first switch 402. The resultant value from the first multiplier 400 is stored in a first delay 404. In a second multiplier 406, the input chrominance signal Cb is also multiplied by xe2x80x9csin xcex8xe2x80x9d applied to the second multiplier 406 in accordance with a switching operation of the second switch 408. The resultant value from the second multiplier 406 is stored in a second delay 410. After completing the multiplication operations for the input chrominance signal Cb, multiplication operations for the input chrominance signal Cr are conducted in the first and second multipliers 400 and 406 using values of xe2x80x9cxe2x88x92sin xcex8xe2x80x9d and xe2x80x9ccos xcex8,xe2x80x9d respectively. After performing the multiplication operation for the input chrominance signal Cr, the resultant product value is outputted from the first multiplier 400 and inputted into a first adder 412 which adds the product value to the value received from the first delay 404, having the input chrominance signal Cb. The resultant value from the first adder 412 is applied to a first input terminal of a third switch 414. Also, after the multiplication operation for the input chrominance signal Cr, the resultant value is outputted from the second multiplier 406 and applied to a second adder 416 which, in turn, adds this value to the value received from the second delay 410, having the input chrominance signal Cb. The resultant value from the second adder 416 is applied to the second input terminal of the third switch 414. Thus, hue-controlled chrominance signals Cb_h and Cr_h are sequentially output in accordance with a switching operation of the third switch 414. The respective values of the output signals from the color hue controller 112 associated with the luminance signal Y and the chrominance signals Cb and Cr can be expressed as follows:
Y=Y
Cbxe2x80x94h=Cbxc3x97cos xcex8xe2x88x92Crxc3x97sin xcex8
Crxe2x80x94h=Cbxc3x97sin xcex8+Crxc3x97cos xcex8xe2x80x83xe2x80x83[Equation 2]
The above Equation 2 may be expressed in the form of a matrix equation as follows:                               [                                                    Y                                                                    Cb_h                                                                    Cr_h                                              ]                =                              [                                                            1                                                  0                                                  0                                                                              0                                                                      cos                    ⁢                                          xe2x80x83                                        ⁢                    θ                                                                                                              -                      sin                                        ⁢                                          xe2x80x83                                        ⁢                    θ                                                                                                0                                                                      sin                    ⁢                                          xe2x80x83                                        ⁢                    θ                                                                                        cos                    ⁢                                          xe2x80x83                                        ⁢                    θ                                                                        ]                    xc3x97                      [                                                            Y                                                                              Cb                                                                              Cr                                                      ]                                              [Equation  2a]            
In the above Equation 2a, xe2x80x9cxcex8xe2x80x9d represents the shift angle of the coordinate axes.
FIG. 6 is a block diagram illustrating a detailed circuit configuration of the flesh tone controller 114. As shown in FIG. 6, the flesh tone controller 114 serves to correct colors near the skin color. When the phase angle of the coordinate axis of the chrominance signal Cr is shifted by an angle of xcex8xe2x80x2, the flesh tone control coefficient used in the flesh tone controller 114 is set to xe2x80x9cxcex8xe2x80x2xe2x80x9d. In this case, a flesh tone control coefficient value of xe2x80x9csin xcex8xe2x80x2xe2x80x9d or xe2x80x9ccos xcex8xe2x80x2xe2x80x9d is input to the flesh tone controller 114 via a first switch 600 which is coupled to those values xe2x80x9csin xcex8xe2x80x2xe2x80x9d and xe2x80x9ccos xcex8xe2x80x2xe2x80x9d associated with the chrominance signals Cb and Cr, respectively. Since the flesh tone controller 114 is adapted to only shift the coordinate axis of the chrominance signal Cr, the chrominance signal Cb, which is inputted to the flesh tone controller 114, is directly applied to a first input terminal of a second switch 602. The chrominance signal Cb is selectively outputted from the flesh tone controller 114, without being changed, in accordance with a switching operation of the second switch 602. The input chrominance signal Cb is also applied to a multiplier 604. In the multiplier 604, the input chrominance signal Cb is multiplied by xe2x80x9csin xcex8xe2x80x2xe2x80x9d applied to the multiplier 604 in accordance with a switching operation of the first switch 600. The resultant value outputted from the multiplier 604 is stored in a delay 606. Subsequently, the chrominance signal Cr, is inputted into the flesh tone controller 114, following the chrominance signal Cb, and is multiplied by xe2x80x9ccos xcex8xe2x80x2xe2x80x9d in the multiplier 604. The resultant value output from the multiplier 604 after the multiplication operation for the input chrominance signal Cr is then applied to an adder 608 for adding to it the value received from the delay 606 associated with the input chrominance signal Cb. The resultant value from the adder 608 is applied to the second input terminal of the second switch 602. The second switch 602 successively outputs from the flesh tone controller 114 the value received from the adder 608 along with the chrominance signal Cb not processed in the flesh tone controller.
The output signal values from the flesh tone controller 114 associated with the luminance signal Y and chrominance signals Cb and Cr, respectively, can be expressed as follows:
xe2x80x83Y=Y
Cbxe2x80x94f=Cb
Crxe2x80x94f=Cbxc3x97sin xcex8xe2x80x2+Crxc3x97cos xcex8xe2x80x2xe2x80x83xe2x80x83[Equation 3]
The above Equation 3 may be expressed in the form of a matrix equation as follows:                               [                                                    Y                                                                    Cb_f                                                                    Cr_f                                              ]                =                              [                                                            1                                                  0                                                  0                                                                              0                                                  1                                                  0                                                                              0                                                                      sin                    ⁢                                          xe2x80x83                                        ⁢                                          θ                      xe2x80x2                                                                                                            cos                    ⁢                                          xe2x80x83                                        ⁢                                          θ                      xe2x80x2                                                                                            ]                    xc3x97                      [                                                            Y                                                                              Cb                                                                              Cr                                                      ]                                              [Equation  3a]            
FIG. 8 is a block diagram illustrating a detailed circuit configuration of the RGB transform unit 116. As shown in FIG. 8, the RGB transform unit 116 processes the chrominance signals Cb_f and Cr_f received from the flesh tone controller 114 along with the luminance signal Y, thereby transforming those signals to an original RGB signal in a conventional fashion. The resultant signals, namely, R, G and B signals, from the RGB transform unit 116 are then sent to the television receiver. That is, the chrominance signal Cr, which is input to the RGB transform unit 116, is multiplied by a gain control coefficient R_GAIN for R-Y chrominance signals in a first multiplier 800. The resultant signal from the first multiplier 800 is applied to a first adder 802 which, in turn, adds that signal to the luminance signal Y applied thereto. The resultant signal from the first adder 802 is output as the R (red) signal. The input chrominance signal Cr is also applied to a second multiplier 808. In the second multiplier 808, the input chrominance signal Cr is multiplied by xe2x80x9cR_COEFxe2x80x9d applied to the second multiplier 808 via a switch 810. The switch 810 is coupled to chrominance signal control coefficients of xe2x80x9cR_COEFxe2x80x9d and xe2x80x9cB_COEFxe2x80x9d for G (green) color values respectively associated with the chrominance signals Cr and Cb in order to selectively apply xe2x80x9cR_COEFxe2x80x9d or xe2x80x9cB_COEFxe2x80x9d to the second multiplier 808 in accordance with its switching operation. The resultant value from the second multiplier 808 is stored in a delay 812. The input chrominance signal Cr is also applied to a third multiplier 804 which, in turn, multiplies the input chrominance signal Cr by a gain control coefficient B_GAIN for B-Y chrominance signals. The resultant signal from the third multiplier 804 is applied to a third adder 806 which, in turn, adds that signal to the luminance signal Y applied thereto. The resultant signal from the third adder 806 is prevented from being output as the B (blue) signal in accordance with a switching operation of a switch (not shown). Subsequently, the chrominance signal Cb, which is inputted into the RGB transform unit 116, following the chrominance signal Cr, is applied to the multipliers 800, 808, and 804, respectively. Although the input chrominance signal Cb applied to the first multiplier 800 is processed in the same manner as that for the chrominance signal Cr applied to the first multiplier 800, its resultant signal is prevented from being outputted from the first adder 802 as the R (red) signal. The input chrominance signal Cb applied to the second multiplier 808 is multiplied by xe2x80x9cB_COEFxe2x80x9d applied to the second multiplier 808 via the switch 810. The resultant value from the second multiplier 808 is then applied to a fourth adder 814 which, in turn, adds that value to the value received from the delay 812 associated with the input chrominance signal Cr. The resultant value from the fourth adder 814 is applied to a second adder 816. In the second adder 816, the signal output from the fourth adder 814 is added to the luminance signal Y applied to the second adder 816. The resultant signal from the second adder 816 is outputted as the G (green) signal. Meanwhile, the input chrominance signal Cb applied to the third multiplier 804 is processed in the same manner as that for the input chrominance signal Cr applied to the third multiplier 804. The resultant signal from the third adder 806 is output as the B (blue) signal. Accordingly, the R, G, and B signals output from the RGB transform unit 116 can be expressed as follows:
R=Y+R_GAINxc3x97Cr
G=Y+B_COEFxc3x97Cb+R_COEFxc3x97Cr
B=Y+B_GAINxc3x97Cbxe2x80x83xe2x80x83[Equation 4]
The above Equation 4 may be expressed in the form of a matrix equation as follows:                               [                                                    R                                                                    G                                                                    B                                              ]                =                              [                                                            1                                                  0                                                  R_GAIN                                                                              1                                                  B_COEF                                                  R_COEF                                                                              1                                                  B_GAIN                                                  0                                                      ]                    xc3x97                      [                                                            Y                                                                              Cb                                                                              Cr                                                      ]                                              [Equation  4a]            
As apparent from the above description, conventional video signal processing devices are equipped with respective circuits for the chrominance signal control and RGB transform functions. When one desires to add another function, it is necessary to provide an additional circuit for performing the added function. For instance, when it is desired to add another chrominance signal control function, a chrominance signal control circuit for the added chrominance signal control function must be provided. Due to the need for an additional chrominance signal control circuit, the entire circuit configuration becomes complex. Furthermore, additional components increase the cost of producing a device.
Accordingly, an object of the invention is to provide a chrominance signal processing apparatus in a video signal processing system which has a simple configuration capable of achieving chrominance signal control and RGB transform functions using a single circuit.
In accordance with the present invention, this object is accomplished by providing a chrominance signal processing apparatus in a video signal processing system comprising: a key input unit provided with a plurality of control keys for chrominance signal controls, the key input unit serving to generate key data in response to a manipulation of desired control keys by the user; a chrominance signal control coefficient computing unit adapted to calculate chrominance signal control coefficients in response to a user""s request for chrominance signal controls received via the key input unit, respectively, the calculation of the chrominance signal control coefficients being carried out in accordance with a matrix computation for variations in chrominance signal coefficients respectively associated with the chrominance signal control coefficients to be calculated; and a chrominance signal control and RGB transform unit adapted to conduct the requested chrominance signal controls for chrominance signals separated from a video signal, along with a luminance signal, by a comb filter of the video signal processing system, based on the chrominance signal control coefficients received from the chrominance signal control coefficient computing unit, and adding the controlled chrominance signals to the luminance signal, respectively, thereby outputting R, G, and B video signals.